Developing method and developing unit

ABSTRACT

In a developing method for performing developing treatment of a substrate by supplying a developing solution onto a resist film formed on a surface of the substrate, the present invention controls a zeta potential of the surface of the substrate at a predetermined potential in the same polarity as that of a zeta potential of insoluble substances floating in the developing solution, thereby preventing or reducing the adhesion of the insoluble substances to the resist film and the substrate. This remedies the occurrence of development defects. The adhesion of the insoluble substances to the resist film and the substrate can also be prevented or inhibited by supplying an acid liquid to a liquid on the substrate, or controlling a pH value of the liquid on the substrate to control an absolute value of the zeta potential of the insoluble substances.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate developing method and asubstrate developing unit.

2. Description of the Related Art

In a photolithography step of semiconductor device fabricatingprocesses, resist coating treatment of applying a resist solution being,for example, a photosensitive resin to a surface of a wafer to form aresist film on the wafer, exposure processing of exposing apredetermined circuit pattern on the wafer on which this resist film isformed, and developing treatment of supplying a developing solution ontothe wafer after the exposure processing to dissolve the resist film atexposed portions are performed in sequence.

In the abovementioned developing treatment, a strong alkaline developingsolution is supplied onto the wafer, and is loaded on the wafer. Then,while this liquid loaded state is maintained for a predetermined periodof time, the wafer is subjected to static development. In this staticdevelopment, a part of the resist film, that is, exposed portions causedto have solubility in the developing solution by the exposure dissolvein the developing solution. When the static development for thepredetermined period of time is finished, the wafer is rotated and acleaning liquid, for example, a pure water is supplied onto the wafer sothat the developing solution is replaced with the pure water.Thereafter, the supply of the pure water is stopped and the wafer isdried by liquid shaking-off by a centrifugal force so that a series ofthe developing treatment is finished.

In the actual static development described above, however, the resistfilm at all the exposed portions does not appropriately dissolve in thedeveloping solution, and so-called insoluble substances which are in aninsoluble state in the developing solution are precipitated in thedeveloping solution from the exposed portions having been subjected toinsufficient exposure, boundaries between the exposed portions given aninsufficient exposure amount and unexposed portions, and so on.

Here, particles of insoluble substances dispersed in a liquid areusually electrically charged, and the electrically charged state of thesurface of the particle (a surface potential) is generally evaluated bya zeta potential. The zeta potential represents a potential near thesurface of the particle, and more precisely, is a potential at a part ofa diffusion layer (sliding surface) on the periphery of a fixed layerformed around the particle in the liquid, with a position at infinityfrom the particle being a reference. Since the zeta potential of theparticle is dependent on the polarity of the liquid surrounding theparticle, it is influenced by the number of ions, that is, a pH value ofthe liquid. Generally, the zeta potential tends to be low in an alkalineliquid due to the existence of many negative ions while, in an acidliquid, it tends to be high due to the existence of many positive ions.

It has been confirmed from experiments conducted by the inventors that,in the above-described developing treatment, the zeta potential of theinsoluble substances floating in the developing solution is negative dueto the strong alkaline developing solution. It has been also confirmedthat the zeta potential of the surface of the wafer in contact with thedeveloping solution is also negatively charged.

The inventors has also confirmed that, when the developing solution isreplaced with the pure water after the pure water is supplied onto therotated wafer as described above, the pH value of the developingsolution drastically lowers, resulting in the increase of the zetapotential of the insoluble substances toward 0 mV. Such decrease in theabsolute value of the zeta potential of the insoluble substances weakensan electrostatic repulsive force between the insoluble substances andthe surface of the wafer, and, in turn, relatively strengthens anintermolecular force to cause adhesion of the insoluble substances ontothe surface of the wafer. Especially, when the absolute value of thezeta potential of the insoluble substances is decreased, the insolublesubstances cohere together to grow into particles having a largerintermolecular force so that they easily adhere onto the wafer.

As a result, the insoluble substances adhering to the wafer cannot beremoved easily even by the wafer cleaning at the time of rinsing, andthe residual insoluble substances have been a cause of developmentdefects. Further, it is necessary to keep supplying the pure water tothe wafer for a long time in order to wash and remove the insolublesubstances adhering to the surface of the wafer, resulting in increasein a total developing time, which lowers a throughput of the wafertreatment.

Further, a resist used in the above-described resist coating treatmentincludes a photoacid generator (PAG) which generates acid when beingirradiated with light. For example, in a positive resist, a protectinggroup having an insolubilizing function in the developing solution andbeing releasable with acid is released therefrom due to the acidgenerated by the exposure, so that the exposed portions thereof arecaused to have solubility in the developing solution. In a negativeresist, the acid generated by the exposure induces a cross-linkingreaction of a resin soluble in the developing solution, and thus theexposed portions thereof are caused to have insolubility in thedeveloping solution. Then, by the supply of the developing solution inthe above-described developing treatment, the exposed portions dissolvein the developing solution in the case of the positive resist while, inthe case of the negative resist, the unexposed portions dissolve in thedeveloping solution with the exposed portions kept undissolved, so thata predetermined resist pattern is formed on the wafer.

Actually, however, a sufficient amount of exposure is not given to theboundaries between the exposed portions and the unexposed portions in achemical point of view. This means that the boundary is inferior insolubility in the developing solution. Further, in the case of, forexample, the positive resist, the surface portions of even the unexposedportions of the resist slightly dissolve in the developing solution.So-called film-reduced portions of the unexposed portions are extremelyinferior in solubility in the developing solution so that they areeasily precipitated in the developing solution. Such existence of theportions inferior in solubility in the developing solution causes, forexample, resist polymers half-released from the protecting group tofloat in the developing solution and, due to the cohesion or the like ofthe resist polymers, these resist polymers thereafter grow into resistparticles, which sometimes adhere to the wafer. This re-adhesion of theresist particles causes development defects and prevents properdeveloping treatment. Moreover, in this case, a sufficient cleaning timeis required for removing the adhering resist particles, resulting in anincrease in a total developing time, which lowers throughput.

In a developing step in the above-described developing treatment, apredetermined portions of the resist film, for example, the exposedportions are dissolved due to the developing solution, and the insolublesubstances which are kept undissolved and float in the developingsolution are rinsed by the pure water in a cleaning step.

However, when the pure water is supplied onto the wafer after theaforesaid static development, the developing solution on the wafer isdiluted so that the pH value of the liquid on the wafer drasticallylowers to be close to neutrality. When the liquid on the wafer thusbecomes closer to neutrality, the zeta potential of the insolublesubstances, for example, the resist particles dispersed in this liquidbecomes closer to 0 mV.

Since the decrease in the absolute value of the zeta potential of theinsoluble substances lowers the electrical repulsive force among theinsoluble substances, the insoluble substances cohere together to growthe particle size of the insoluble substances. The insoluble substanceswhose particle size has grown turn into impurities liable to influencethe developing treatment, which has been a cause of the developmentdefects.

Moreover, when the insoluble substances cohere together, they easilyadhere to the wafer and the resist film. It can be reasoned that thisadhesion is caused because an intermolecular force among the insolublesubstances is strengthened. The insoluble substances once adhering ontothe wafer and so on cannot be removed easily even when the wafer isrotated in an attempt to shake them off by the centrifugal force, andthe residual insoluble substances have been a cause of the developmentdefects. In addition, the pure water needs to be kept supplied to thewafer for a long time in order to remove the adhering insolublesubstances from the surface of the wafer and so on.

SUMMARY OF THE INVENTION

The present invention is made in consideration of the abovecircumstances, and an object thereof is to prevent the adhesion ofinsoluble substances floating in a developing solution onto the surfaceof a substrate such as a wafer, thereby reducing development defects anda developing treatment time. Another object of the present invention isto sufficiently secure solubility in the developing solution ofpredetermined portions of a resist, thereby performing proper developingtreatment. Still another object of the present invention is to preventthe insoluble substances floating in the developing solution fromcohering together.

In order to attain these objects, in a developing method of the presentinvention, developing treatment is performed by controlling a zetapotential of a substrate surface to be a predetermined potential in thesame polarity as that of a zeta potential of insoluble substancesfloating in a developing solution.

According to another aspect, in a developing method of the presentinvention, a charged member electrically charged in an opposite polarityto that of a zeta potential of insoluble substances floating in adeveloping solution is brought into contact with the developingsolution.

According to still another aspect, in a developing method of the presentinvention, a charged member electrically charged to the same polarity asthat of a zeta potential of insoluble substances floating in adeveloping solution is brought into contact with the developing solutionon the substrate and the charged member is moved.

According to yet another aspect, in a developing method of the presentinvention, a potential gradient is given to a substrate supplied with adeveloping solution, and a potential of the substrate is cocentricallychanged with time.

According to yet another aspect, in a developing method of the presentinvention, a developing solution is supplied onto a resist film whilethe resist film is set to a room temperature or higher, for example, 25°C. to 100° C., more preferably, 40° C. to 80° C.

According to yet another aspect, in a developing method of the presentinvention, a developing solution is supplied onto a resist film while asubstrate is set to a room temperature or higher, for example, 40° C. to200° C., more preferably, 40° C. to 160° C.

According to yet another aspect, a developing method of the presentinvention has a first step of loading a developing solution on asubstrate, a second step of subjecting the substrate to staticdevelopment while the developing solution is loaded on the substrate,and a third step of supplying a cleaning liquid to the substrate toclean the substrate after the static development, and between the secondstep and the third step, the substrate is supplied with a liquid largerin specific gravity than the cleaning liquid, for forming a liquid layerbetween the developing solution and a surface of a resist film.

According to yet another aspect, in a developing method of the presentinvention, an ionic surfactant having a predetermined polarity is addedto a developing solution, and the ionic surfactant is made to adhere toinsoluble substances floating in the developing solution and a surfaceof a substrate.

According to yet another aspect, a developing method of the presentinvention is a developing method for performing developing treatment ofa substrate by applying a resist solution onto a surface of a substrateto form a resist film and supplying a developing solution onto theformed resist film, in which the resist solution is applied to thesurface of the substrate, with an ionic surfactant in a predeterminedpolarity being mixed in the resist solution.

According to yet another aspect, a developing method of the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution onto a resist film formedon a surface of the substrate, in which an ionic surfactant in apredetermined polarity is supplied onto a surface of the resist filmbefore the developing solution is supplied.

A polymer nonionic surfactant may be used in place of the ionicsurfactant.

According to yet another aspect, in a developing method of the presentinvention, when a resist film formed on a surface of a substrate hasconductivity, a voltage is applied to this resist film to keep thisresist film at a potential in the same polarity as that of insolublesubstances in a developing solution at least during developingtreatment.

A developing unit of the present invention is a developing unitperforming developing treatment of a substrate by supplying a developingsolution onto a resist film formed on a surface of the substrate, andhas a charging unit electrically charging the surface of the substrateto a zeta potential in a predetermined polarity.

According to yet another aspect, a developing unit of the presentinvention has an ion atmosphere supply section supplying a periphery ofa substrate with an atmosphere including ions in a predeterminedpolarity.

According to yet another aspect, a developing unit of the presentinvention has a charged member electrically chargeable to apredetermined polarity and a charged member carrier carrying the chargedmember to bring the charged member into contact with a developingsolution on a substrate.

According to yet another aspect, a developing unit of the presentinvention has a surfactant supply section supplying an ionic surfactantin a predetermined polarity onto a substrate.

According to yet another aspect, a developing unit of the presentinvention has a surfactant supply section supplying a nonionicsurfactant onto a substrate.

According to yet another aspect, a developing unit of the presentinvention has a charging unit electrically charging a developingsolution to a zeta potential in a predetermined polarity.

According to yet another aspect, a developing unit of the presentinvention has a charged member electrically charged to the same polarityas that of insoluble substances in a developing solution loaded on aresist film on a surface of a substrate, and a moving member moving thecharged member above the substrate.

According to yet another aspect, a developing unit of the presentinvention has a plurality of electrodes disposed cocentrically on anupper surface of a mounting table on which a substrate is to be placed,a power supply applying a voltage to each of the electrodes, and acontrol section changing a potential of each of the electrodes withtime.

According to yet another aspect, a developing unit of the presentinvention has a heating unit heating a substrate.

According to yet another aspect, a developing unit of the presentinvention has a mounting table supporting a substrate by clamping and aunit applying a voltage to a resist film on a substrate placed on themounting table.

According to the present invention, since the adhesion of the insolublesubstances floating in the developing solution to the surface of thesubstrate can be prevented or inhibited, proper developing treatment isachieved and yields are improved. Further, since the cleaning timeduring the developing treatment can be shortened, enhancement inthroughput of substrate treatment is achieved.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidliquid is supplied to the substrate at a stage prior to the supply ofthe developing solution to the substrate after the substrate is coatedwith the resist.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidliquid is supplied to the substrate after the developing solution issupplied to the substrate.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidliquid is supplied to the substrate when the developing solution iswashed away by a cleaning liquid after the developing treatment isperformed by supplying the developing solution to the substrate.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidliquid is supplied to the substrate after the developing solution iswashed away by a cleaning liquid after the developing treatment isperformed by supplying the developing solution to the substrate, andthereafter, the cleaning liquid is supplied again to the substrate forcleaning.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidgas is supplied to the substrate at a stage prior to the supply of thedeveloping solution to the substrate after the resist is applied to thesubstrate.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidgas is supplied to the substrate after the developing solution issupplied to the substrate.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate by supplying a developing solution to the substrate coatedwith a resist and exposed in a predetermined pattern, in which an acidgas is supplied to the substrate after the developing solution is washedaway by a cleaning liquid after the developing treatment is performed bysupplying the substrate with the developing solution, and thereafter,the cleaning liquid is supplied again to the substrate for cleaning.

According to yet another aspect of the present invention, the presentinvention is a developing unit performing developing treatment of asubstrate by supplying a developing solution to the substrate coatedwith a resist and having undergone exposure, and has an acid liquidsupply section supplying an acid liquid to the substrate.

According to yet another aspect of the present invention, the presentinvention is a developing unit performing developing treatment of asubstrate by supplying a developing solution to the substrate coatedwith a resist and having undergone exposure, and has an acid gas supplysection supplying an acid gas to the substrate.

According to the present invention, solubility in the developingsolution of a predetermined portion of the resist can be ensured so thatthe predetermined portion of the resist appropriately dissolves in thedeveloping solution to enable the formation of a desired resist pattern.This can enhance yields. Further, the insoluble substances do not floatin the developing solution and thus the re-adhesion of the insolublesubstances to the substrate can be prevented, so that a cleaning timefor removing the adhering insoluble substances can be shortened andenhancement in throughput can be also achieved.

According to yet another aspect of the present invention, the presentinvention is a developing method for performing developing treatment ofa substrate having: a developing step of developing the substrate bysupplying a developing solution onto the substrate on which a resistfilm is formed; and a cleaning step of supplying a cleaning liquid ontothe substrate to clean the substrate after the developing step, and a pHvalue of a liquid on the substrate during the cleaning step is adjustedto such a pH value that an absolute value of a zeta potential ofinsoluble substances floating in the liquid becomes a maximum value.

The pH value of the liquid on the substrate during the cleaning step maybe adjusted to such a pH value that the absolute value of the zetavoltage of the insoluble substances floating in the liquid becomes equalto or larger than a set value and the set value may be defined as avalue equal to or larger than a minimum value with which the insolublesubstances start to cohere together.

According to yet another aspect, the present invention is a developingunit performing a developing step of supplying a developing solution toa substrate and thereafter, a cleaning step of supplying a cleaningliquid to the substrate, and has a pH adjusting liquid supply sectionsupplying a pH adjusting liquid onto the substrate in order to adjust apH value of a liquid on the substrate during the cleaning step.

The inventors of the present invention has confirmed that a pH value ofa liquid and a zeta potential of insoluble substances in the liquid hasa certain correlation. According to the present invention, the pH valueof the liquid on the substrate is so adjusted in the cleaning step thatthe absolute value of the zeta potential of the insoluble substancesbecomes the maximum value, and consequently, it is possible to preventthe insoluble substances from cohering together due to a decreasedabsolute value of the zeta potential of the insoluble substances duringthe cleaning step. Accordingly, neither the growth of the particle sizeof the insoluble substances nor the adhesion of the insoluble substancesto the substrate or the like is caused, which enables reduction indevelopment defects. Further, substances precipitated from the resistfilm, substances originally existing in the liquid, and substancesentering the liquid from the outside may also be treated as theinsoluble substances.

Moreover, when the pH value of the liquid on the substrate during thecleaning step is adjusted and the absolute value of the zeta voltage ofthe insoluble substances is maintained at a value equal to or a largerthan a predetermined value with which the insoluble substances do notcohere together, the growth of the particle size of the insolublesubstances can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an external appearance of a coating anddeveloping system having a developing unit where a developing methodaccording to an embodiment is performed;

FIG. 2 is a front view of the coating and developing system in FIG. 1;

FIG. 3 is a rear view of the coating and developing system in FIG. 1;

FIG. 4 is an explanatory view of a side section of the developing unit;

FIG. 5 is an explanatory view of a horizontal section of the developingunit;

FIG. 6 is a perspective view of a spin chuck of the developing unit;

FIG. 7 is a perspective view of a developing solution supply nozzle;

FIG. 8 is a vertical sectional view of a side surface of the developingsolution supply nozzle in FIG. 6;

FIG. 9 is a flowchart of developing treatment;

FIG. 10 is an explanatory view of a vertical section of a wafer, showingthe state of electrical charges when the wafer is electrically charged;

FIG. 11 is an explanatory view of a vertical section of the wafer,showing the state of insoluble substances in a developing solution;

FIG. 12 is an explanatory view of a horizontal section of a developingunit having a charged member;

FIG. 13 is an explanatory view showing the structure of a supportingarm;

FIG. 14 is a flowchart of developing treatment using the charged member;

FIG. 15 is an explanatory view of a vertical section of the wafer,showing the state of insoluble substances when the charged member isbrought into contact with the developing solution;

FIG. 16 is an explanatory view of a vertical section, showing thestructure of a developing unit having an ionizer;

FIG. 17 is an explanatory view of a horizontal section, showing thestructure of a developing unit having a surfactant supply nozzle;

FIG. 18 is a flowchart of developing treatment in which a surfactant issupplied;

FIG. 19 is an explanatory view of a vertical section of the wafer,showing the state of the wafer when an ionic surfactant is addedthereto;

FIG. 20 is an explanatory view of the vertical section of the wafer,showing the state of the wafer when a nonionic surfactant is addedthereto;

FIG. 21 is an explanatory view showing the structure of a supply systemof the surfactant supply nozzle;

FIG. 22 is an explanatory view showing the structure of a supply systemof another surfactant supply nozzle;

FIG. 23 is a side sectional view of a developing unit having a unitheating a substrate;

FIG. 24 is a plan view of a unit in which a charged member is attachedto the developing solution supply nozzle;

FIG. 25 is a plan view showing the state in which the charged member inFIG. 24 is scan-moved together with the developing solution supplynozzle above the wafer;

FIG. 26 is a side view showing the state in which the charged member inFIG. 24 is scan-moved together with the developing solution supplynozzle above the wafer;

FIG. 27 is a plan view of a spin chuck having zone electrodes;

FIG. 28 is an explanatory view showing a potential gradient given to asubstrate through the use of the zone electrodes;

FIG. 29 is an explanatory view showing how potential values are changedwith time by controlling the zone electrodes;

FIG. 30 is an explanatory view showing a wave motion due to thepotential change with time;

FIG. 31 is an explanatory view showing the structure for applying avoltage to a pipe of the developing solution supply nozzle;

FIG. 32 is an explanatory view showing the structure for applying avoltage to a resist film on the wafer;

FIG. 33 is a side sectional view of a developing unit having a nozzlefor supplying the wafer with a liquid larger in specific gravity thanthe developing solution;

FIG. 34 is an explanatory view showing the state after the liquid largerin specific gravity than the developing solution is supplied to thedeveloping solution on the resist film;

FIG. 35 is an explanatory view of a vertical section of a developingunit in another embodiment;

FIG. 36 is an explanatory view of a horizontal section of the developingunit in FIG. 35;

FIG. 37 is an explanatory view showing an elimination reaction of aprotecting group of a resist to which hydrogen fluoride is added;

FIG. 38 is a flowchart of developing treatment;

FIG. 39 is a flowchart showing another example of the developingtreatment;

FIG. 40 is an explanatory view of a horizontal section of a developingunit according to still another embodiment;

FIG. 41 is an explanatory view showing an example of an acid gassupplying unit;

FIG. 42 is an explanatory view of a horizontal section of a developingunit in yet another embodiment;

FIG. 43 is an explanatory view showing a supply system of a cleaningliquid supply nozzle;

FIG. 44 is a graph showing a correlation curve between a zeta potentialof insoluble substances in a liquid and a pH value of the liquid;

FIG. 45 is an explanatory view of a horizontal section showing adeveloping unit when it has a pH adjusting liquid supply nozzle; and

FIG. 46 is an explanatory view showing supply systems of the pHadjusting liquid supply nozzle and a pure water supply nozzle in FIG.45.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be explained below.FIG. 1 is a plan view schematically showing the structure of a coatingand developing system 1 having a developing unit where a developingmethod according to this embodiment is performed, FIG. 2 is a front viewof the coating and developing system 1, and FIG. 3 is a rear view of thecoating and developing system 1.

As shown in FIG. 1, the coating and developing system 1 has a structurein which integrally connected are a cassette station 2 for carrying, forexample, 25 wafers W from/to the outside to/from the coating anddeveloping system 1 in the unit of cassette and for carrying the wafersW into/from a cassette C, a processing station 3 in which various kindsof processing units for performing predetermined processing wafer bywafer in a coating and developing step are disposed in multi-tiers, andan interface section 4 provided adjacent to the processing station 3,for receiving and delivering the wafer W from/to a not-shown aligner.

In the cassette station 2, the plural cassettes C are mountable atpredetermined positions on a cassette mounting table 5, which serves asa mounting section, in a line in an X-direction (a vertical direction inFIG. 1). Further, a wafer carrier 7, which is transferable in thiscassette arrangement direction (the X-direction) and in a waferarrangement direction of the wafers W housed in the cassette C (aZ-direction; a perpendicular direction), is provided to be movable alonga carrier guide 8 so that it is structured to be able to selectivelyaccess each of the cassettes C.

The wafer carrier 7 has an alignment function of aligning the wafer. W.This wafer carrier 7 is structured to be capable of also accessing anextension unit 32 belonging to a third processing unit group G3 on theside of the processing station 3 as will be described later.

In the processing station 3, a main carrier 13 is provided in a centerpart thereof, and various kinds of the processing units are multi-tieredon the periphery of the main carrier 13 to constitute processing unitgroups. In the coating and developing system 1, four processing unitgroups G1, G2, G3 and G4 are disposed, and the first and secondprocessing unit groups G1 and G2 are disposed on a front side of thecoating and developing system 1, the third processing unit group G3 isdisposed adjacent to the cassette station 2, and the fourth processingunit group G4 is disposed adjacent to the interface section 4. Further,as an option, a fifth processing unit group G5 depicted by a broken linecan be additionally arranged on a rear side. The main carrier 13 cancarry the wafer W into/from various kinds of the later-describedprocessing units disposed in these processing unit groups G1, G2, G3,G4, and G5. Incidentally, the number and the arrangement of theprocessing unit groups vary depending on the kind of the processinggiven to the wafer W and the number of the processing unit groups can beselected freely as long as it is one or more.

In the first processing unit group G1, for example, as shown in FIG. 2,a resist coating unit 17 applying a resist solution onto the wafer W toform a resist film on the wafer W and a developing unit 18 according tothis embodiment are two-tiered in this order from the bottom. Similarly,in the second processing unit group G2, a resist coating unit 19 and adeveloping unit 20 are two-tiered in this order from the bottom.

In the third processing unit group G3, for example, as shown in FIG. 3,a cooling unit 30 for cooling the wafer W, an adhesion unit 31 forincreasing fixability between the resist solution and the wafer W, theextension unit 32 for delivering the wafer W thereto and therefrom,pre-baking units 33 and 34 for evaporating a solvent in the resistsolution, and a post-baking unit 35 for performing heating processingafter the developing treatment are, for example, six-tiered in thisorder from the bottom.

In the fourth processing unit group G4, for example, a cooling unit 40,an extension and cooling unit 41 for spontaneously cooling the placedwafer W, an extension unit 42, a cooling unit 43, post-exposure bakingunits 44 and 45 for performing heating processing after exposureprocessing, and a post-baking unit are, for example, seven-tiered inthis order from the bottom.

In a center part of the interface section 4, for example, a wafercarrier 50 is provided as shown in FIG. 1. This wafer carrier 50 isstructured to be movable in the X-direction (the vertical direction inFIG. 1) and the Z-direction (the perpendicular direction), and to berotatable in a O-direction (a rotational direction about an axis Z), sothat it can access the extension and cooling unit 41 and the extensionunit 42 which belong to the fourth processing unit group G4, an edgeexposure unit 51, and the not-shown aligner to carry the wafer W to eachof them.

Next, the structure of the aforementioned developing unit 18 will beexplained in detail. As shown in FIG. 4 and FIG. 5, a spin chuck 60serving as a holding member for holding the wafer W by suction isprovided in a casing 18 a of the developing unit 18. On an upper surfaceof the spin chuck 60, a thin disk-shaped electrode plate 61 is attachedas shown in FIG. 6. As a material of the electrode plate 61, aconductive material, for example, iron or copper is used. The electrodeplate 61 has a horizontal upper surface and a suction port 62 isprovided in the electrode plate 61, so that the spin chuck 60 is capableof making the wafer W adhere to the electrode 61 by suction from thesuction port 62 to hold the wafer W horizontally.

A conducting wire 63 connected to a direct-current power supply 64 isattached to, for example, a lower surface of the electrode plate 61 sothat a voltage can be applied to the electrode plate 61. In other words,the electrode plate 61 can be electrically charged by the application ofa direct-current voltage to the electrode plate 61. The voltage of thedirect-current power supply 64 and the polarity thereof can becontrolled by a control section 65 so that the electrode plate 61 can beelectrically charged to a predetermined potential in a predeterminedpolarity. As a result, it is made possible to induce electrons insidethe wafer W held on the electrode plate 61 by suction, therebycontrolling a zeta potential of a surface of the wafer W at apredetermined potential in a predetermined polarity. Incidentally, acharging unit in this embodiment is composed of the electrode plate 61,the conducting wire 63, the direct-current power supply 64, and thecontrol section 65. The direct-current power supply 64 and the controlsection 65 constitute a voltage applying means in this embodiment.

A drive mechanism 65 for driving this spin chuck 60 is disposed, forexample, under the spin chuck 60 as shown in FIG. 4. The drive mechanism65 includes a rotation drive section (not shown), which is provided witha motor or the like, for rotating the spin chuck 60 at a predeterminedrotation speed, and a hoisting and lowering drive section (not shown),which is provided with a motor, a cylinder, or the like, for verticallymoving the spin chuck 60. A hoisting and lowering mechanism of this spinchuck 60 is intended for carrying the wafer W to/from the main carrier13.

Outside the spin chuck 60, a ring-shaped cup 70 whose upper surface isopen is provided, surrounding the spin chuck 60. This cup 70 receives adeveloping solution and so on scattering from the wafer W which is heldon and rotated by the spin chuck 60, thereby preventing contamination ofsurrounding equipment. To a bottom surface of the cup 70, a drainpipe 71for draining out the developing solution and so on scattering from thewafer W and so on and an exhaust duct 72 for exhausting an atmosphereinside the cup 70 are connected.

Outside this cup 70, a square outer cup 75 whose upper surface is openis provided, surrounding the cup 70, to receive the developing solutionand so on from the wafer W, which the cup 70 fails to receive, therebyenabling the prevention of the developing solution and so on fromscattering. Incidentally, a not-shown drive mechanism allowing the outercup 75 to move in the vertical direction is provided in the outer cup75, and for example, it moves up when the wafer W is to be cleaned sothat a scattered cleaning liquid and so on can be more surely collected.

As shown in FIG. 5, a stand-by section T is provided outside the outercup 75, for example, outside on a negative direction side of an Mdirection (a left side in FIG. 5), and in this stand-by section T, adeveloping solution supply nozzle 80 for supplying the developingsolution to the wafer W can stand by.

The developing solution supply nozzle 80 has a long and narrow shape asshown in FIG. 7, and a length L thereof is larger at least than thediameter of the wafer W. To an upper part of the developing solutionsupply nozzle 80, a pipe 81 communicating with a not-shown developingsolution supply source is connected. In a lower part of the developingsupply nozzle 80, a plurality of developing solution supply ports 82 aredisposed in a line in a longitudinal direction. Further, inside thedeveloping solution supply nozzle 80, a solution reservoir section 83elongated in the longitudinal direction and communicating with each ofthe developing solution supply ports 82 and the pipe 81 is formed, asshown in FIG. 8 so that the developing solution flowing into thedeveloping solution supply nozzle 80 from the pipe 81 can be temporarilystored therein and the developing solution can be discharged from eachof the developing solution supply ports 82 simultaneously at the sameflow rate and at the same pressure.

As shown in FIG. 5, the developing solution supply nozzle 80 issupported by an arm 85, and this arm 85 is movable on a rail 86 laid inthe M direction (a right and left direction in FIG. 5) by a not-shownmoving mechanism. The rail 86 extends from the stand-by section T to theoutside of the outer cup 75 on a positive direction side of the Mdirection so that the developing solution supply nozzle 80 is movable atleast from the stand-by section T to the outside of the cup 70 on thepositive direction side of the M direction. The developing solutionsupply nozzle 80 is supported by the arm 85 with the longitudinaldirection thereof being perpendicular to the M direction, and when thedeveloping solution supply nozzle 80 moves above the wafer W whiledischarging the developing solution from each of the developing solutionsupply ports 82 of the developing solution supply nozzle 80, thedeveloping solution can be supplied to the whole surface of the wafer W.Incidentally, a not-shown hoisting and lowering mechanism, which isprovided in the arm 85, is capable of vertically moving the developingsolution supply nozzle 80 when necessary, thereby enabling the transferof the developing solution supply nozzle 80 into/out of alater-described cleaning bath 87 of the stand-by section T, theadjustment of the distance thereof from the wafer W, and so on.

The stand-by section T has the cleaning bath 87 in which the developingsolution supply nozzle 80 is cleaned. This cleaning bath 87 has aconcave shaped cross section so as to accommodate the developingsolution supply nozzle 80 in the long and narrow shape, and in thiscleaning bath 87, a predetermined solvent for washing away thedeveloping solution adhering to the developing solution supply nozzle 80can be stored.

A stand-by section U for a cleaning liquid supply nozzle 90 forsupplying a cleaning liquid to the wafer W is provided outside the outercup 75 on the positive direction side of the M direction (the right sidein FIG. 5). The cleaning liquid supply nozzle 90 is supported by a rinsearm 91, and this rinse arm 91 is movable on the rail 86 on which, forexample, the aforesaid arm 85 also moves. The cleaning liquid supplynozzle 90 is supported by the rinse arm 91 so as to be able to supplythe cleaning liquid to the center part of the wafer W when it istransferred to a position above the wafer W in the cup 70. In thestand-by section U, provided is a cleaning bath 92, for example, for thecleaning liquid supply nozzle 90, and when the cleaning liquid supplynozzle 90 is immersed in the cleaning bath 92 storing, for example, asolvent, impurities adhering to the cleaning liquid supply nozzle 90 canbe removed.

A transfer port 100 through which the wafer W is carried into/out of thedeveloping unit 18 is provided in a side surface of the casing 18 a, andthis transfer port 100 can be opened and closed freely by a shutter 101.

Next, a developing method carried out in the developing unit 18 asstructured above will be explained along with processes of aphotolithography step performed in the coating and developing system 1.

First, one unprocessed wafer W is taken out from the cassette C by thewafer carrier 7 and carried to the extension unit 32 belonging to thethird processing unit group G3. Next, the main carrier 13 carries thewafer W into the adhesion unit 31 where, for example, HMDS forincreasing fixability of the resist solution is applied onto the waferW.

Next, the wafer W is carried to the cooling unit 30, where it is cooledto a predetermined temperature, and is thereafter carried to the resistcoating unit 17. In the resist coating unit 17, for example, a positiveresist solution which is a photosensitive resin is supplied to the waferW so that a resist film is formed on the wafer W. Thereafter, the waferW is carried by the main carrier 13 to the pre-baking unit 33 and theextension and cooling unit 41 in sequence, and further carried by thewafer carrier 50 to the edge exposure unit 51, thereby undergoingpredetermined processing in each of the units. Next, the wafer W iscarried to the aligner (not shown), where a predetermined circuitpattern is exposed on the wafer W by, for example ultravioletirradiation. At this time, exposed portions of the resist film becomesoluble in an alkaline solution. The wafer W having undergone theexposure processing is carried to the extension unit 42 by the wafercarrier 50, and thereafter, after undergoing predetermined processing inthe post-exposure baking unit 44 and the cooling unit 43, the wafer W iscarried to the developing unit 18, where it undergoes the developingtreatment.

The wafer W having undergone the developing treatment in the developingunit 18 is carried to the post-baking unit 46 and the cooling unit 30 insequence to undergo predetermined processing in each of the units, andthereafter, is returned to the cassette C via the extension unit 32 sothat a series of the photolithography step is finished.

Next, the developing treatment performed in the abovementioneddeveloping unit 18 will be explained in detail. FIG. 9 shows a flowchartof this developing treatment. In this embodiment, a strong alkalineaqueous solution, for example, TMAH(N(CH₃)₄OH) or the like of, forexample, about pH 13 is used as the developing solution.

First, the wafer W is carried through the transfer port 100 into thecasing 18 a by the main carrier 13 and held on the spin chuck 60 bysuction (Step S1). When the wafer W is held by suction, the developingsolution supply nozzle 80 in the stand-by section T moves to a startposition S inside the cup 70 near an edge portion of the wafer W on thenegative direction side of the M direction (Step S2). Next, while thedeveloping solution supply nozzle 80 is kept unmoved at the startposition S, the discharge of the developing solution is started andso-called predispense is performed until the discharge condition of thedeveloping solution from each of the developing solution supply ports 82is stabilized (Step S3).

Then, before proceeding to the subsequent Step S4, a cathodic voltage isapplied to the electrode plate 61 on the spin chuck 60 by thedirect-current power supply 64, and the electrode plate 61 is negativelycharged as shown in FIG. 10.

As a result, a lower surface of the wafer W in contact with theelectrode plate 61 is positively charged by electrostatic induction andan upper surface of the wafer W is negatively charge. Accordingly, azeta potential of the surface of the wafer W becomes negative.Meanwhile, a lower part of a resist film R with the wafer W serving as abase thereof is positively charged and an upper part thereof isnegatively charged. The control section 65 adjusts the voltage of thedirect-current power supply 64, thereby controlling the zeta potentialof the surface of the wafer W to be a predetermined set potential, forexample, about −70 mV.

Incidentally, the polarity of the voltage applied to the electrode 61 isdetermined so as to be the same polarity as that of a zeta potential oflater-described insoluble substances Y of the resist film R in thedeveloping solution. The polarity of the zeta potential of the insolublesubstances is obtained in advance, for example, by an experiment or thelike, and the zeta potential of the insoluble substances in thisembodiment is −20 mV in the developing solution of, for example, pH 13.As the set voltage of the surface of the wafer W, an optimum voltage atwhich the insoluble substances stop adhering to the surface of the waferW is obtained in advance, for example, by an experiment or the like foreach kind of the resist film and each kind of the developing solutionand this obtained voltage is stored, for example, in the control section65. Incidentally, it is also suitable that an adhesion amount or thelike of the insoluble substances to the surface of the wafer W ismeasured after the developing treatment and the set potential is changedbased on this measurement value.

After the discharge condition from the developing solution supply nozzle80 is stabilized and the wafer W is electrically charged, the developingsolution supply nozzle 80 moves to the positive direction side of the Mdirection while discharging the developing solution, passes above thewafer W, and moves up to an end position E near an edge portion of thewafer W on the positive direction side of the M direction. Through thisoperation, a predetermined amount of loading of the developing solutionis formed on the wafer W (Step S4), and the wafer W is subsequentlysubjected to static development for a predetermined period of time (StepS5).

As shown in FIG. 11, this supply of the developing solution causes mostof the resist film R at the exposed portions to dissolve in thedeveloping solution and other portions are partly precipitated and floatin the developing solution as the insoluble substances Y. The insolublesubstances Y have a negative zeta potential as described above to causea repulsive force against the surface of the wafer W similarlynegatively charged and the insoluble resist film R. As a result, theinsoluble substances Y do not adhere to the surface of the wafer W andthe insoluble portions of the resist film R. Incidentally, thedeveloping solution supply nozzle 80 which stops moving in the endposition E stops discharging the developing solution and is returned tothe stand-by section T. Note that a first step and a second stepcorrespond to Step S4 and Step S5 respectively in this embodiment.

Subsequently, when the static development for the predetermined periodof time is finished, the cleaning liquid supply nozzle 90 moves to aposition above the center part of the wafer W and discharges thecleaning liquid, for example, a pure water onto the wafer W (Step S6).The wafer W is rotated concurrently with the supply of, for example,this pure water and the developing solution on the wafer W is replacedwith the pure water. At this time, pH of the developing solution on thewafer W drastically lowers to become close to pH 7, that is, neutrality.At this time, the zeta potential, which is −20 mV, of the insolublesubstances lowers to, for example −60 mV to increase an absolute valueof the zeta potential so that the tendency that the insoluble substancesY adhere to the surface of the wafer W is weakened compared with that atthe time of the static development. Note that a third step correspondsto Step S6 in this embodiment.

The wafer W is kept rotated even after the developing solution isreplaced with the pure water so that the insoluble substances Y on thewafer W are thoroughly removed (Step S7). Thereafter, the discharge ofthe pure water is stopped and the wafer W is rotated at a high speed sothat the wafer W is dried by liquid shaking-off (Step S8). For example,when this drying processing of the wafer W is finished, the applicationof the voltage to the electrode plate 61 is finished and the electriccharge electrically charging, for example, the wafer W is grounded.Then, the wafer W is delivered to the main carrier 13 from the spinchuck 60 to be carried out of the developing unit 18 (Step S9) so that aseries of the developing treatment is finished.

According to the above-described embodiment, the electrode plate 61 isprovided on the spin chuck 60 holding the wafer W thereon, and the zetapotential of the surface of the wafer W is made to have a negativepolarity which is the same as that of the insoluble substances Y in thedeveloping solution so that the repulsive force constantly acts betweenthe insoluble substances Y and the surface of the wafer W. Further,since the absolute value of the zeta potential of the surface of thewafer W is set to a sufficiently large value, a strong repulsive forceis maintained between the insoluble substances Y and the surface of thewafer W even when the zeta potential of the insoluble substances Yfluctuates. This can prevent or inhibit the adhesion of the insolublesubstances Y to the surface of the wafer W.

Moreover, since the zeta potential of the surface of the wafer W iscontrolled over the period before Step S4 where the insoluble substancesY occur in the developing solution to Step S where the insolublesubstances Y on the wafer W are removed, the adhesion of the insolublesubstances Y can be completely prevented.

In the developing method described in the above embodiment, the surfaceof the wafer W serving as the base of the resist film R is electricallycharged to a predetermined polarity, but the developing solutionsupplied onto the wafer W may be brought into contact with a chargedmember electrically charged to a predetermined polarity.

FIG. 12 shows an example of a developing unit 110 realizing such adeveloping method, in which a charged member 111 is on stand-by in astand-by section K, for example, on a positive direction side of an Mdirection of an outer cup 75. The charged member 111 is formed, forexample, in a disk shape similarly to the wafer W, and as a materialthereof, for example, metal such as iron and copper excellent inconductivity is used. A conducting wire 113 connected to, for example, adirect-current power supply 112 is attached to an upper surface of thecharged member 111, so that the polarity and amount of electric chargeto be applied to the charged member 111 by a control section 114 of thedirect-current power supply 112 can be adjusted.

The charged member 111 is supported by a supporting arm 115 serving as acharged member carrying means. The supporting arm 115 is movable in theM direction on a rail 116 laid from the stand-by section K to thevicinity of a cup 70, thereby enabling the charged member 111 to move toa position above the wafer W in the cup 70. Further, as shown in FIG.13, the supporting arm 115 has a cylinder 117 serving as a hoisting andlowering mechanism, which enables the vertical movement thereof.Therefore, the charged member 111 is capable of descending after movingto the position above the wafer W from the stand-by section K, andapproaching the wafer W so as to coincide in position with the surfaceof the wafer W. A cleaning bath 118 in which the charged member 111 isimmersed, for example, in a predetermined solution for cleaning isprovided in the stand-by section K. The cleaning bath 118 has, forexample, the same shape as that of the charged member 111, that is, forexample, a circular shape in its plan view. Incidentally, other membersof the developing unit 110 are the same as those of the developing unit18, and therefore, the explanation thereof will be omitted.

In developing treatment in this developing unit 110, for example, asshown in FIG. 14, the charged member 111, for example, positivelycharged is carried from the stand-by section K to a position facing thewafer W after Step S4 of loading the developing solution is finished, sothat the charged member 111 is brought into contact with the developingsolution on the wafer W. When static development for a predeterminedperiod of time in Step S5 is performed in this state, the insolublesubstances Y having a negative zeta potential, which are precipitatedfrom the resist film R, are attracted to the charged member 111 toadhere to the charged member 111, as shown in FIG. 15. When the staticdevelopment is finished, the charged member 111 which has collected alarge amount of the insoluble substances Y retreats from the wafer W tobe returned to the stand-by section K. The charged member 111 returnedto the stand-by section K is immersed in the cleaning bath 118 and theinsoluble substances Y are washed away.

According to this embodiment, the charged member 111 electricallycharged to an opposite polarity to that of the insoluble substances Y isbrought into contact with the developing solution on the wafer W so thatthe insoluble substances Y in the developing solution adhere to thecharged member 111, thereby enabling the charged member 111 to collectthe insoluble substances Y Consequently, the adhesion of the insolublesubstances Y to the surface of the wafer W can be prevented.

Further, the supporting arm 115 may be moved to actively move thecharged member 111, thereby promoting the adhesion of the insolublesubstances Y in the developing solution to the charged member 111.

The charged member 111 may have a shape other than a circular shape, forexample, a square shape or the like. Further, the adhesion of theinsoluble substances Y to the wafer W may be prevented by, instead ofthe use of the charged member 111, supplying the periphery of thesurface of the wafer W with an ion atmosphere having the same polarityas that of the insoluble substances Y and electrically charging thesurface of the wafer W to a predetermined polarity.

In such a case, an ionizer 121 serving as an ion atmosphere supplysection which supplies the ion atmosphere including ions in apredetermined polarity is provided in a casing 120 a in a developingunit 120, for example, as shown in FIG. 16. The inside of the casing 120a is kept under a negative ion atmosphere at least during the periodfrom the occurrence of the insoluble substances Y to the removal of theinsoluble substances Y. This ion atmosphere causes the surface of thewafer W to be negatively charged, thereby enabling the prevention of theadhesion of the insoluble substances Y, which is negatively charged, tothe surface of the wafer W. Incidentally, the ionizer 121 may bedisposed on an upstream side of an air current inside the developingunit 120 to supply the negative ion atmosphere more efficiently to thewafer W. Further, an ionizer utilizing corona discharge or soft X-raysmay be used as the ionizer 121. Moreover, though such an ionizer is ameans mainly for electrically charging a gas, a means for electricallycharging vapor, mist, and the like may be used.

Instead of bringing the charged member 111 into contact with thedeveloping solution, an ionic surfactant in a predetermined polarity maybe added into the developing solution to prevent the adhesion of theinsoluble substances Y to the surface of the wafer W.

FIG. 17 shows an example of a developing unit 130 realizing developingtreatment in such a case, and, for example, a surfactant supply nozzle131 serving as a surfactant supply section which supplies the ionicsurfactant is provided in the developing unit 130 . . . . Thissurfactant supply nozzle 131 is supported by, for example, a nozzle arm132, and this nozzle arm 132 is provided to be movable on a rail 133extending in an M direction. The rail 133, which is laid on an oppositeside of a rail 86, for example, for the developing solution supplynozzle 80 across a cup 70, enables the surfactant supply nozzle 131 tomove to a position above the center of the wafer W on a spin chuck 60.

In the developing treatment in this developing unit 130, the ionicsurfactant is supplied to the wafer W immediately after the developingsolution is loaded on the wafer W in Step S4, for example, as shown inFIG. 18. The surfactant supplied onto the wafer W adheres to thesurfaces of the wafer W, the resist film R, and the insoluble substancesY, as shown in FIG. 19. As a result, the surface of the wafer W, theinsoluble substances Y, and so on which are covered with ions in thesame polarity, for example, negative ions repel one another to preventthe adhesion of the insoluble substances Y to the surface of the wafer Wand so on. Further, in this case, the surfactant is supplied when theinsoluble substances Y begin to occur, thereby enabling the surerprevention of the adhesion of the insoluble substances Y to the surfaceof the wafer and so on. Incidentally, the surfactant may be suppliedeither immediately before Step S4 or in Step S4.

The ionic surfactant may be supplied onto the wafer W also when a purewater is supplied in Step S6. The supply of the pure water compensatesfor the decreasing negative ions on the surface of the wafer W so thatit is made possible to prevent the insoluble substances Y from adheringto the surface of the wafer W and so on at the time of cleaning.Incidentally, the ionic surfactant may be supplied only when the purewater is supplied in Step S6. This is superior in that the property ofthe developing solution is not at all influenced by the surfactant atthe time of the static development in Step S5.

Further, the surfactant supply nozzle 131 may have the same structure asthat of the aforementioned developing solution supply nozzle 80 tosupply the surfactant to the entire surface of the wafer W byscan-moving.

A polymer nonionic surfactant may be supplied onto the wafer W insteadof the ionic surfactant. The polymer nonionic surfactant is, in itsnature, absorbed to particles in a liquid, and a repulsive force isgenerated in tiered polymer layers resulting from this absorption, andas a result, the polymer nonionic surfactant has a function of improvingdispersion stability of the particles. It is reasoned that this functionis caused by an osmotic pressure effect or a capacity control effect ofthe polymer nonionic surfactant. Therefore, when the nonionic surfactantis supplied into the developing solution on the wafer W, the nonionicsurfactant is absorbed to the insoluble substances Y, the surface of thewafer W, and the surface of the resist film R, as shown in FIG. 20,thereby enabling the prevention of the insoluble substances Y to thesurface of the wafer W and so on owing to the dispersion stabilizingeffect. Incidentally, as the nonionic surfactant, for example,polyoxyethylene alkylether, polyoxyalkylene alkylether, or the like isused.

As shown in FIG. 21, a concentration adjusting unit 142 capable ofadjusting the concentration of the surfactant may be provided in asupply pipe 141 connecting the surfactant supply nozzle 131 and a buffertank 140 for the surfactant. The concentration of the surfactantsupplied onto the wafer W is varied depending on the kind of the resistfilm, the kind of the developing solution, and so on. For example, whenthe insoluble substances Y have a relatively small absolute value in itszeta potential and thus easily cohere together, the concentration of thesurfactant is set to a value in a higher range. This setting causes moreof the surfactant to be absorbed to the insoluble substances Y and thesurface of the wafer W, resulting in the increase in the repulsive forcebetween, for example, the insoluble substances Y and the surface of thewafer W so that the adhesion of the insoluble substances Y can beappropriately prevented.

Incidentally, such a method is also adoptable that an optimumconcentration of the surfactant causing the decrease in the adhesionamount of the insoluble substances Y is obtained for each kind of theresist film and the developing solution in advance by an experiment orthe like, this optimum concentration is stored in the concentrationadjusting unit 142 or the like, and the concentration of the surfactantis adjusted to this optimum concentration. Further, the concentrationadjusting unit 142 may be a unit performing concentration adjustment bymixing a solvent, an amount of which is predetermined according to theset concentration, into the surfactant passing through, for example, thesupply pipe 141.

The surfactant may be supplied onto the wafer W from the aforesaiddeveloping solution supply nozzle 80. In this case, such a structure mayalso be adopted, for example, as shown in FIG. 22 that a branch pipe 153communicating with a buffer tank 152 for the surfactant is attached to asupply pipe 151 communicatingly connecting the developing solutionsupply nozzle 80 and a developing solution storage tank 150, and athree-way valve 154 is provided at a connection part between the branchpipe 153 and the supply pipe 151. This three-way valve 154 allowsselective supply of the developing solution and the surfactant to thedeveloping solution supply nozzle 80, and allows the discharge of thesurfactant onto the wafer W at a predetermined timing as describedabove. Further, the surfactant may be added into the developingsolution, and in this case, a predetermined amount of the surfactant maybe added to the developing solution in advance or the surfactant may beadded to the developing solution in the supply pipe 151 where thedeveloping solution is on its way to be sent to the developing solutionsupply nozzle 80.

In the above-described embodiment, the surfactant is mixed in thedeveloping solution or the surfactant is added thereto when thedeveloping solution is loaded on the wafer W, but alternatively, thesurfactant or vapor or mist of the surfactant may be supplied onto thewafer W before the developing solution is supplied onto the wafer W.This method can also inhibit the adhesion of the insoluble substances toa substrate.

The aforesaid surfactant may be mixed in the resist solution in advance,and the resist solution with the surfactant being thus mixed therein maybe applied when the resist solution is applied to the wafer W in theresist coating units 17 and 19. This method can also inhibit theadhesion of the insoluble substances to the substrate.

Conventionally, the developing treatment is performed while thetemperature of the wafer W and the temperature of the developingsolution supplied to the wafer W are maintained at a room temperature,for example, around 23° C., but when, in the developing treatment, thetemperature of the wafer W or the temperature of the developing solutionis set to a room temperature or higher, for example, 25° C. to 80° C.,more preferably 40° C. to 60° C. for the developing solution, and 40° C.to 200° C., more preferably 40° C. to 160° C. for the wafer W, theadhesion of the insoluble substances floating in the developing solutionto the resist film can be inhibited. This is because, in the case whenthe repulsive force between the zeta potential of the insolublesubstances and the potential of the resist film is weak, this repulsiveforce can be increased by increasing the temperature of the substrate orthe developing solution.

As described above, since the conventional developing unit performs thesubstrate treatment at a room temperature, a unit for increasing thetemperature of the substrate is not provided in the unit. Here, a unitshown in, for example, FIG. 23 can be proposed in order to perform thedeveloping treatment by increasing the temperature of the substrate asproposed in the present invention.

In this unit shown in FIG. 23, a lamp heating unit 161 is provided on aceiling section inside the casing 18 a. This makes it possible to heat,for example, the wafer W up to the room temperature or higher, forexample, 40° C. to 200° C., more preferably 40° C. to 160° C. when thedeveloping treatment of the wafer W is performed.

Incidentally, the temperature of the developing solution supplied to thewafer W can be raised by raising the temperature of a temperatureadjusting fluid in a: temperature adjusting mechanism conventionallyused for the developing solution supply nozzle 80, for example, amechanism which supplies the temperature adjusting fluid to the nozzleto adjust the temperature of the developing solution.

Next, explanation will be given on an example of using a charged memberin the same polarity as that of the zeta potential of the insolublesubstances in the developing solution.

FIG. 24 shows a plan view of an example of such a unit, in which acharged member 171 is attached to the developing solution supply nozzle80 via a bracket 172 to be in parallel to this developing solutionsupply nozzle 80, with a certain distance being kept therefrom. Thecharged member 171 is set to the same length as that of the developingsolution supply nozzle 80, and a lower surface thereof is also set tothe same height position as that of the developing solution supplynozzle 80. A voltage from a power supply 173 is applied to the chargedmember 171. This enables the charged member 171 to be electricallycharged to the same polarity as that of the zeta potential of theinsoluble substances in the developing solution.

The charged member 171 thus electrically charged to the same polarity asthat of the zeta potential of the insoluble substances is used in thefollowing manner. Specifically, after the developing solution is loadedon the wafer W by the developing solution supply nozzle 80, the arm 85is moved so that the charged member 171 is scan-moved together with thedeveloping solution supply nozzle 80 above the wafer W as shown in FIG.25 and FIG. 26. At this time, the charged member 171 is brought intocontact with a developing solution DL on the wafer W as shown in FIG.26.

This causes the insoluble substances floating in the developing solutionDL to move since they repel the charged member 171. The scan-move ofthis charged member 171 causes the insoluble substances to move in thedeveloping solution DL and to be forced out from the edge portion of thewafer W together with the developing solution DL. Therefore, in thisexample, a considerable number of the insoluble substances are forcedout of the wafer W together with the developing solution DL, through theuse of the repellency between the charged member 171 and the insolublesubstances. As a result, the adhesion of the insoluble substances to theresist film and the wafer W is inhibited.

Incidentally, in the case when the charged member 171, which is chargedto the same polarity as that of the zeta potential of the insolublesubstances in the developing solution, is moved as described above, thewafer W is preferably charged to the same polarity as that of the zetapotential of the insoluble substances as well. This is because, in thismanner, the insoluble substances and the wafer W also repel each otherso that the insoluble substances can be prevented from coming closer tothe wafer W side. Consequently, the adhesion of the insoluble substancesto the resist film and the wafer W can be more effectively prevented.Incidentally, the wafer W can be electrically charged to the samepolarity as that of the zeta potential of the insoluble substances byusing, for example, the direct-current power supply 64.

Moreover, in the case when the charged member 171 and the wafer W areelectrically charged to the same polarity, the wafer W is preferablyelectrically charged so as to cause a potential of the wafer W to becomehigher than a potential of the charged member 171. This is because theinsoluble substances are further prevented from coming closer to thewafer W side.

Another example shown in FIG. 27 can also be proposed. FIG. 27 shows anexample of concentrically disposing zone electrodes 181, 182, and 183 onthe surface of the spin chuck 60. The spin chuck 60 is the same in sizeas the wafer W placed thereon. The zone electrodes 181, 182, and 183 arearranged at predetermined spaced intervals. The zone electrodes 181,182, and 183 are respectively connected to power supplies 184, 185, and186 which apply voltages thereto, and a control unit 187 controlsapplication timing and values of the applied voltages. The voltages canbe applied in a pulsed manner. Note that CEN represents the center ofthe wafer W and EDG represents an edge portion of the wafer W in thedrawing.

Such a unit is used in the following manner. Specifically, as shown inFIG. 28, through the control by the control unit 187, for example, aregion in the wafer W corresponding to the zone electrode 183 positionedat the utmost outer circumference is positively charged, a regioncorresponding to the zone electrode 182 on an inner side is thennegatively charged, and a region corresponding to the zone electrode 181positioned at the center part is more negatively charged, thereby givinga potential gradient to the wafer W.

The voltage application from, for example, the zone electrodes 182 and183 is controlled in this state to change the value of the appliedvoltage to each of these electrodes at every predetermined timing asshown in FIG. 29. For example, a strong voltage and a weak voltage arealternately applied to the zone electrodes 182 and 183. Note that thevertical axis represents a potential level in FIG. 29. At this time, theregions corresponding to the zone electrodes 182 and 183 are keptnegatively charged.

When a time series potential change is thus caused in each of theregions in the wafer W by controlling the voltage application to thezone electrodes 181, 182, and 183, a wave motion is generated due topotential shift as shown in FIG. 30, so that the insoluble substances,which are in the developing solution on the wafer W, at a negativelycharged zeta potential are forced out toward an outer circumference sideof the wafer W due to the wave motion.

Thereafter, the developing solution is shaken off from the outercircumference of the wafer W by the rotation of the spin chuck 60 or thelike, so that the adhesion of the insoluble substances to the resistfilm on the wafer W can be prevented.

A voltage may be applied to the developing solution which is to besupplied from the developing solution supply nozzle 80, at the stageprior to the discharge thereof from the developing solution supplynozzle 80. For example, as shown in FIG. 31, a pipe including aconductive material is used as a pipe 191 which constitutes a part of asupply pipe connected to the developing solution supply nozzle 80, andinsulating members 192 and 193 are disposed in both end portionsthereof. A power supply 194 applies a voltage to this pipe 191. Withthis structure, the developing solution DL is electrically charged whenit passes through the pipe 191 and the developing solution DL kept inthis state is supplied to the wafer W from the developing solutionsupply nozzle 80.

When the developing solution DL is electrically charged to the samepolarity as that of the zeta potential of the insoluble substances, therepellency due to the same polarity can prevent the adhesion of theinsoluble substances to the resist film even when the insolublesubstances occur in the developing solution supplied onto the resistfilm on the wafer W at the developing treatment stage.

When the resist film formed on the wafer W has conductivity, this resistfilm itself is electrically charged so that the aforesaid repellency dueto the same polarity can inhibit the adhesion of the insolublesubstances floating in the developing solution to the resist film.

FIG. 32 shows a structure example when a voltage is thus applied to aresist film 201 on the wafer W, in which a clamp 203 is attached to anouter edge portion of a mounting table 202, for example, a spin chuck orthe like for supporting the wafer W. This clamp 203 directly clamps anedge portion of the wafer W to support the wafer W on the mounting table202. A power supply 204 applies a voltage to this clamp 203 itself or anelectrode (not shown) disposed together with the clamp 203, therebyenabling the resist film 201 to be electrically charged at a potentialin a predetermined polarity.

A liquid, for example, HFE (hydrofluoroether) larger in specific gravitythan the developing solution and giving no influence to a developingreaction may be supplied into the developing solution on the wafer W atthe stage prior to the cleaning of the wafer W after the developingsolution is supplied to the wafer W and the static development isfinished. This can be achieved by providing in the developing unit 18 anozzle 211 supplying this liquid, for example, as shown in FIG. 33.

When the liquid larger in specific gravity than the developing solutionis thus supplied into the developing solution, a layer 212 of thisliquid can be formed between the resist film R and the developingsolution DL in which the insoluble substances are floating, as shown inFIG. 34. This layer 212 can prevent the insoluble substances in thedeveloping solution DL from adhering to the resist film R.

In the above-described embodiment, the present invention is applied tothe developing method of the wafer W, but the present invention is alsoapplicable to developing methods of substrates other than semiconductorwafers, for example, LCD substrates and mask reticle substrates forphotomask.

As explained hitherto, according to the present invention, the zetapotential of the substrate surface is controlled to be a predeterminedpotential in the same polarity as that of the zeta potential of theinsoluble substances in the developing solution, which enables thegeneration of a sufficient electrical repellent force between theinsoluble substances and the substrate surface. Accordingly, theadhesion of the insoluble substances to the substrate can be preventedand development defects caused by this adhesion are reduced. Further, acleaning time can be shortened owing to no adhesion of the insolublesubstances so that a developing treatment time can be shortened.Incidentally, the substrate surface may also include a base of theresist film and an anti-reflection film, and the base may be either anoxide film or another kind of film. Moreover, the zeta potential of thesubstrate surface may be so controlled that the absolute value of thezeta potential of the substrate surface becomes 30 mV or larger. Notethat the ‘insoluble substances’ dealt with in the present invention maybe either those precipitated from the resist film or those entering thedeveloping solution from the outside though originally existing in thedeveloping solution.

As is previously stated, the developing treatment has the first step ofloading the developing solution on the substrate, the second step ofsubjecting the substrate to the static development while the developingsolution is loaded thereon, and the third step of supplying the cleaningliquid to the substrate having undergone the static development to cleanthe substrate, and the zeta potential of the substrate surface may becontrolled over the period from the first step to the third step. Theinsoluble substances of the resist film begin to occur when the supplyof the developing solution to the substrate is started and keep existingon the substrate until the substrate is cleaned. Therefore, the controlof the potential of the substrate surface over the period from the firststep to the third step as in this developing method makes it possible tomore surely inhibit the adhesion of the insoluble substances to thesubstrate surface.

When the charged member electrically charged to an opposite polarity tothat of the zeta potential of the insoluble substances floating in thedeveloping solution is brought into contact with the developingsolution, the insoluble substances in the developing solution areabsorbed to the charged member to enable the collection of the insolublesubstances. This can inhibit the adhesion of the insoluble substances tothe substrate surface.

When the charged member is brought into contact with the developingsolution at the time of the static development in which the insolublesubstances occur most, the insoluble substrates can be collected by thecharged member more effectively. When the charged member is brought intocontact with the developing solution only in the second step, the supplyof the developing solution and so on conducted by, for example, nozzlesor the like in the first step can be carried out without being disturbedby the charged member.

The adhesion of the ionic surfactant so as to cause the substratesurface and the insoluble substances to be in the same polarity canprevent the adhesion of the insoluble substances to the substratesurface owing to the repulsive force generated between the substratesurface and the insoluble substances. As a result, development defectscaused by the adhesion of the insoluble substances to the substratesurface can be reduced. Further, since the insoluble substances do notadhere to the substrate surface, the cleaning time is shortened,resulting in the reduction in the developing time.

The polymer nonionic surfactant may be added to the developing solution,in place of the ionic surfactant. The polymer nonionic surfactant isabsorbed to particles and so on in a liquid and the repulsive force isgenerated in the tired polymer layers resulting from this absorption,and consequently, the polymer nonionic surfactant improves thedispersion stability of the particles and so on in the liquid. In thepresent invention, the nonionic surfactant is absorbed to the insolublesubstances in the developing solution and the substrate surface throughthe use of this dispersion stabilizing effect, thereby forming acovering film on the insoluble substances and the substrate surface sothat the adhesion between the insoluble substances and the substratesurface can be prevented.

The surfactant may be added in the first step. Note that the first stepincludes immediately before the first step and immediately after thefirst step. In such a developing method, since the surfactant is addedto the developing solution in the first step when the insolublesubstances begin to occur, the adhesion of the insoluble substances tothe substrate surface can be prevented until the substrate is thereaftercleaned. Therefore, the adhesion of the insoluble substances to thesubstrate surface is more surely prevented.

The surfactant may be added not only in the first step but also in thethird step. In the third step, the cleaning liquid is supplied onto thesubstrate to temporarily lower the concentration of the surfactant.According to this invention, since the surfactant is newly added in thethird step to compensate for the decreased surfactant, which makes itpossible to more surely prevent the residual insoluble substances on thesubstrate from adhering to the substrate.

The surfactant may be added only in the third step. The addition of thesurfactant into the developing solution causes a slight change inquality of the developing solution. The addition of the surfactant notduring the static development but at the time of the cleaning as in thepresent invention allows the static development to be free of theinfluence given by the addition of the surfactant, and also makes itpossible to inhibit the adhesion of the insoluble substances to thesubstrate surface.

According to the developing unit of the present invention, a chargingmeans is capable of electrically charging the zeta potential of thesubstrate surface to a predetermined potential in the same polarity asthat of the zeta potential of the insoluble substances in the developingsolution so that the electrical repulsive force can be generated betweenthe insoluble substances and the substrate surface, thereby making itpossible to prevent or inhibit the adhesion of the insoluble substancesto the substrate surface. As a result, development defects of thesubstrate caused by the adhesion of the insoluble substances can bereduced. Further, since the insoluble substances do not adhere to thesubstrate surface, the time required for the cleaning process which iscarried out after the static development of the substrate can beshortened so that the total developing treatment time can be shortened.

The provision of the control section which controls the voltage to beapplied to the electrode plate enables free control of the zetapotential of the substrate surface in contact with the electrode plate.Consequently, the zeta potential of the substrate surface can becontrolled to be such a potential in the same polarity as that of thezeta potential of the insoluble substances, having a repulsive forcepreventing the adhesion of the insoluble substances to the substratesurface.

Further, when the charged member is electrically charged to an oppositepolarity to that of the zeta potential of the insoluble substancesfloating in the developing solution and is brought into contact with thedeveloping solution, the insoluble substances floating in the developingsolution are attracted and collected by the charged member. As a result,the adhesion of the insoluble substances to the substrate surface can beprevented. Incidentally, the charged member may have the same shape asthat of the substrate so as to be able to collect the insolublesubstances from the entire surface of the substrate.

According to the present invention, since the adhesion of the insolublesubstances floating in the developing solution to the substrate surfacecan be prevented, the developing treatment is rationalized to improveyields. Further, since the cleaning time of the developing treatment canbe shortened, the throughput of the substrate processing is improved.

Next, another embodiment will be explained. A developing solution supplynozzle 80 supplying a developing solution to a wafer W can stand by in astand-by section T in a casing 18 a of a developing unit 218 shown inFIG. 35 and FIG. 36. In this embodiment, an alkaline aqueous solution,for example, TMAH(N(CH₃)₄OH) or the like is used as the developingsolution.

A stand-by section K is disposed outside an outer cup 75 on a positivedirection side of an M direction (a right side in FIG. 36), and an acidliquid supply nozzle 280 serving as an acid liquid supply sectionsupplying an acid liquid, for example, hydrogen fluoride to the wafer Wis on stand-by in this stand-by section K. The acid liquid supply nozzle280 is formed in, for example, a cylindrical shape and is capable ofdischarging downward the hydrogen fluoride supplied from a not-shownhydrogen fluoride supply source.

The acid liquid supply nozzle 280 is supported by, for example, a nozzlearm 281, and this nozzle arm 281 is provided to be movable on a straightrail 282 extending in the M direction. The rail 282 is provided, forexample, on an opposite side of a rail 86 for a developing solutionsupply nozzle 80 across a cup 70, and is laid from the stand-by sectionK to the vicinity of an edge portion of the cup 70 on a negativedirection side of the M direction. The nozzle arm 281 supports the acidliquid supply nozzle 280 in such a manner that the acid liquid supplynozzle 280 passes above a center part of the cup 70. Therefore, the acidliquid supply nozzle 280 is capable of moving from the stand-by sectionK to a position above the center part of the wafer W on a spin chuck 60.

The rail 282 may be provided on the same side as the rail 86 relative tothe cup 70. A storage tank 283 storing, for example, a predeterminedsolvent is provided in the stand-by section K so that the acid liquidsupply nozzle 280 can be cleaned while a tip portion thereof is immersedin the solvent when it is on stand-by. This can prevent the acid liquidsupply nozzle 280 from being corroded by hydrogen fluoride.

A developing method carried out in a developing unit 218 as structuredabove will be explained.

In the resist coating unit 17 where resist coating is carried out, aliquid positive resist including a polyvinyl phenol resin (beforereaction in FIG. 37), for example, as shown in FIG. 37, a photoacidproducing agent, an acid diffusion inhibitor, and so on is applied ontothe wafer W, the polyvinyl phenol resin having a protecting group R(refer to a left side in FIG. 37), so that a resist film is formed onthe wafer W. Incidentally, as the protecting group R, selected is, aspreviously described, a protecting group releasable with acid, having aninsolubilizing function in the developing solution, for example, at-butoxy carbonyl oxy group, an isoproxy carbonyl group, atetrahydropyranyl group, a trimethylsilyl group, a t-butoxy carbonylmethyl group, or the like.

Then, the wafer W on which the resist film is formed is carried to thealigner (not shown), where the wafer W is irradiated with a light in apredetermined pattern. This light irradiation causes acid from thephotoacid producing agent to be produced in the resist film at exposedportions, and the protecting group R in the resist film at the exposedportions is released from the principal chain due to this acid, and issubstituted for by a hydroxyl group at these portions (refer to a rightside in FIG. 37). The resist including this hydroxyl group hassolubility in the alkaline developing solution.

Thereafter, after undergoing predetermined processing in thepost-exposure baking unit 44 and the cooling unit 43, the wafer W iscarried to the developing unit 218 to undergo developing treatment.

The developing treatment performed in the developing unit 218 will beexplained with reference to a flowchart in FIG. 38.

First, the wafer W is carried into the casing 18 a through a transferport 100 by the main carrier 13 and held on the spin chuck 60 by suction(Step S1). When the wafer W is held by suction, the acid liquid supplynozzle 280 moves to the position above the center part of the wafer W.At this time, the rotation of the wafer W is started at a predeterminedrotation speed. Then, a predetermined amount of the hydrogen fluoride isdischarged from the acid liquid supply nozzle 280 to the center part ofthe rotated wafer W so that the hydrogen fluoride is supplied to theentire surface of the wafer W (Step S2).

In Step S2, a protecting group R connected to a principal chain of theresist is released by acid of the hydrogen fluoride and is substitutedfor by a hydroxyl group at this portion, as shown in FIG. 37. Thiscauses the release of the protecting group R in surface layers ofunprocessed portions, that is, portions which are to be precipitated inthe developing solution by the supply of the developing solutionthereafter. This further causes the release of the protecting group R inboundaries between the exposed portions having undergone insufficientexposure and the unexposed portions. As a result, solubility of theresist in the developing solution in the boundaries with the surfacelayers of the unprocessed portions is improved. Incidentally, in theexposed portions, there sometimes remains the resist in which anelimination reaction of the protecting group R cannot be caused at thetime of the exposure processing, and the supply of this hydrogenfluoride also causes the elimination reaction of the protecting group Rof these exposed portions.

After a predetermined period of time elapses after the hydrogen fluorideis supplied to the wafer W, the rotation of the wafer W is stopped andthe acid liquid supply nozzle 280 is returned to the stand-by section KSubsequently, the developing solution supply nozzle 80 moves to a startposition S inside the cup 70 near an edge portion of the wafer W on thenegative direction side of the M direction, and moves from this startposition S to an end position E near an edge portion of the wafer W onthe positive direction side of the M direction while discharging thedeveloping solution (Step S3).

By this operation, a predetermined amount of the developing solution isloaded on the wafer W and the static development for a predeterminedperiod of time is started. In this static development, the resist in theexposed portions dissolves in the developing solution. Further, thesurface layer portions of the unexposed portions and the boundariesbetween the exposed portions and the unexposed portions, where theprotecting group R is released by the acid supply, also dissolve in thedeveloping solution. Meanwhile, portions of the unexposed portion otherthan the surface layer portions do not dissolve in the developingsolution since they have the protecting group R. Thus, a predeterminedresist pattern is formed on the wafer W.

When static development for a predetermined period of time is finished,a cleaning liquid supply nozzle 90 moves to the position above thecenter part of the wafer W and the wafer W is rotated, so that acleaning liquid, for example, a pure water is supplied to the wafer Wfrom the cleaning liquid supply nozzle 90 (Step S4). The developingsolution on the wafer W is replaced with the pure water and the useddeveloping solution is removed from the surface of the wafer W.Thereafter, the discharge of the pure water is stopped, the wafer W isrotated at a high speed, and the wafer W is dried by liquid shake-off(Step S5). When this drying process is finished, the wafer W isdelivered from the spin chuck 60 to the main carrier 13, and is carriedout of the developing unit 218 (Step S6), so that a series of thedeveloping treatment is finished.

According to this embodiment, since the hydrogen fluoride being an acidliquid is supplied onto the wafer W before the developing solution issupplied thereto, the protecting group R connected to the principalchain of the resist is released and substituted for by the hydroxylgroup in the surface layers of the unexposed portions when thedeveloping treatment is started, thereby enabling the increase insolubility in the developing solution of the surface layers of theunexposed portions. Further, since, in the boundaries between theexposed portions having undergone an insufficient amount of exposure andthe unexposed portions, the elimination reaction of the protecting groupR can be promoted, solubility in the developing solution of theboundaries can be enhanced. Consequently, such a state does not occurthat insoluble resist polymers disperse from the surface layers of theunexposed portions and the boundaries to float in the developingsolution, which was conventionally the case, thereby making it possibleto prevent resist particles whose particle size has grown due tocohesion of the resist polymers from re-adhering to the wafer W.Therefore, development defects caused by the re-adhesion of theinsoluble substances such as the resist particles to the substrate canbe reduced. In addition, a cleaning time for removing the adheringinsoluble substances is not necessary, thereby enabling the reduction inthe total developing treatment time.

In this embodiment, the developing solution is supplied immediatelyafter the hydrogen fluoride is supplied to the wafer W, but thedeveloping solution may be supplied after the wafer W supplied with thehydrogen fluoride is cleaned.

For example, after Step S2 in which the hydrogen fluoride is supplied isfinished, the cleaning liquid supply nozzle 90 moves to the positionabove the center part of the wafer W to supply the rotated wafer W withthe cleaning liquid, for example, the pure water (Step S2′), as shown inFIG. 39. The hydrogen fluoride on the wafer W is replaced with the purewater and is removed from the wafer W. In this case, it can be avoidedthat the acid liquid remains on the wafer W to give an adverse effect toa physical property of the developing solution which is to be suppliedthereafter or to react with the developing solution, thereby producingimpurities.

In the above-described embodiment, the hydrogen fluoride being the acidliquid is supplied before the developing solution is supplied to thewafer W, but the acid liquid may be supplied after the developingsolution is supplied. In this case, the developing treatment isperformed in the order of, for example, the supply of the developingsolution, the supply of the acid liquid, and the supply of the purewater. Also in the case where the acid liquid is thus supplied after thedeveloping solution is supplied, the insoluble resist polymers dispersedin the developing solution from the boundaries between the exposedportions and the unexposed portions and the surface layers of theunexposed portions are changed to be soluble, so that it can beprevented that the resist polymers cohere together thereafter to growthe particle size thereof and adhere to the wafer W. Incidentally, thedeveloping solution may be further supplied after the supply of the acidliquid subsequent to the supply of the developing solution and the purewater may be supplied thereafter.

Moreover, it is also suitable that the acid liquid is supplied after thecleaning liquid is supplied and the cleaning liquid is further suppliedthereafter for cleaning. Further, the acid liquid may be suppliedconcurrently at the time of rinsing with the cleaning liquid. In thiscase, the cleaning liquid may be supplied from the cleaning liquidsupply nozzle 90 while the acid liquid is supplied from the acid liquidsupply nozzle 280, or a liquid made by mixing the acid liquid and thecleaning liquid in advance may be supplied to the wafer W by connectinga pipe for the acid liquid which is connected to the acid liquid supplynozzle 280 to a pipe for the cleaning liquid.

The acid liquid supply nozzle 280 in the above-described embodimentsupplies the hydrogen fluoride to the center part of the wafer W, but itmay the one having the same structure as that of the developing solutionsupply nozzle 80 and supplying the acid liquid to the entire surface ofthe wafer W by scan-moving above the wafer W. In this case, similarly tothe aforesaid developing solution supply nozzle 80, the acid liquidsupply nozzle 280 moves from one end portion of the wafer W to the otherend portion thereof while discharging the hydrogen fluoride from aplurality of supply ports to supply the hydrogen fluoride to the entiresurface of the wafer W. In this example, since the wafer W need not berotated when the hydrogen fluoride is being supplied, only a smallamount of the hydrogen fluoride is wasted, thereby enabling thereduction in a consumption amount of the hydrogen fluoride.

In the above-described embodiment, the acid liquid is supplied to thecenter part of the wafer W through the use of the acid liquid supplynozzle 280, but an acid gas supply nozzle 293 supplying an acid gas tothe wafer W may be used as shown in FIG. 40.

In the example in FIG. 40, the acid gas supply nozzle 293 is connectedto an acid gas supply source 294, for example, a gas cylinder or thelike so that the acid gas, for example, a chlorine gas can be suppliedto the wafer W from the acid gas supply nozzle 293.

When the acid gas is thus supplied instead of supplying the acid liquidto the wafer W, the same effect as that brought about by the supply ofthe acid liquid is also obtainable, so that the occurrence of theinsoluble substances can be inhibited.

Incidentally, when, at the time of the supply of the acid liquid and thesupply of the acid gas, the wafer W as the substrate is heated inadvance to a room temperature or higher for example, 25° C. to 80° C.,more preferably, 40° C. to 60° C. to be in a higher temperature range,solubility is further increased so that the occurrence of the insolublesubstances can be inhibited. In the case of supplying the acid liquid,the same effect is also obtainable when the supplied acid liquid itselfis heated to a higher temperature range equal to or higher than a roomtemperature, for example, 25° C. to 80° C., more preferably 40° C. to60° C. and this heated acid liquid is supplied to the wafer W.

The substrate such as the wafer W can be heated by providing a heatingunit 295 such as a heater in the spin chuck 60 or providing a heatingunit 296 such as a lamp on the ceiling portion inside the casing 18 a,for example, as shown in FIG. 40. Incidentally, in the case of providingthe heating unit 295 in the spin chuck 60, the spin chuck 60 preferablyhas the same size as that of the wafer W or larger.

In the example in FIG. 40, the acid gas supply nozzle 293 is directlyconnected to the acid gas supply source 294 to supply the gas such as achloride gas which itself has acidity, but such a structure is alsoadoptable that, as shown in FIG. 41, the acid liquid is stored in a tank297, an inert carrier gas, for example, a gas from a gas supply source298 such as a nitrogen gas or an argon gas is supplied into the tank 297to bubble the acid liquid in the tank 297, and mist or vapor of the acidliquid generated at this time is sent to the acid gas supply nozzle 293by this carrier gas. Such a structure enables the supply of a gascontaining the mist or vapor of the acid liquid to the wafer W.

In the above-described embodiment, the resist applied to the wafer W isthe positive resist, but the present invention is also applicable to thecase where the resist film is a negative resist, for example, a resistcomposed of a base resin+a photoacid producing agent+an acid-reactivecross-linking agent. This negative resist is insolbilized in thedeveloping solution by a cross-linking reaction induced by acid. In thisnegative resist, the cross-linking reaction which is only insufficientlycaused at the time of the exposure processing is induced by the supplyof the acid at the time of the developing treatment so that solubilityin the developing solution of the exposed portions is sufficientlylowered. Consequently, the resist at the exposed portions surely remainsand only the resist at the unexposed portions dissolves in thedeveloping solution, thereby forming a desired resist pattern.

As is explained hitherto, according to the present invention, the acidliquid is supplied so that the action of the acid can change solubilityin the developing solution of the resist. More specifically, solubilityof the resist at the boundaries between the exposed portions and theunexposed portions can be increased. Further, solubility of the resistat the surface layers of the unexposed portions can be increased.Accordingly, the insoluble substances such as the resist particles donot float in the developing solution which is supplied thereafter andthus the re-adhesion of the insoluble substances to the substrate iseliminated, which makes it possible to reduce development defects causedby the adhesion of the insoluble substances.

The acid liquid used in the present invention may be either organic acidor inorganic acid and, for example, hydrogen fluoride, hydrochloricacid, nitric acid, and a diluted liquid of each of them can be proposed.Incidentally, the stage prior to the supply of the developing solutionto the substrate after the resist is applied thereto may be the stageeither after the exposure or before the exposure as long as it is priorto the supply of the developing solution after the resist is formed.

The substrate may be cleaned (rinsed in a generally used term) after theacid liquid is supplied at the stage prior to the supply of thedeveloping solution to the substrate after the resist is appliedthereto. In this case, since the acid liquid supplied onto the substrateis removed from the surface of the substrate and the developing solutionis supplied thereafter, for example, the influence given to the propertyof the developing solution by the acid can be avoided. Further, it canbe also prevented that the developing solution reacts with the residualacid to produce impurities.

A liquid containing a large amount of hydroxyl group or hydrogen (forexample, a bubbled ozonized water with acid being mixed therein) may beused instead of the acid liquid, even if it is neutral. This is becausethe use of such a liquid increases solubility of the resist so that theoccurrence of the insoluble substances such as particles can be furtherinhibited.

The resist may be the positive resist including the protecting groupreleasable with acid, which has an insolubilizing function in thedeveloping solution. In this case, the supply of the acid promotes therelease of the protecting group to increase solubility of the resistpolymers which are dispersed in the developing solution due to, forexample, the so-called film-thickness reduction mentioned above. As aresult, neither of such states arises, that is, the state that theresist polymers inferior in solubility do not dissolve in the developingsolution to float therein, and the state that the resist particles andso on cohering together re-adhere to the substrate.

Still another embodiment will be explained. FIG. 42 shows a developingunit 318 for carrying out a developing method according to the otherembodiment. As a developing solution used in this embodiment, a strongalkaline developing solution of about pH 13, for example,TMAH(N(CH₃)₄OH) or the like is supplied from a developing solutionsupply nozzle 80.

A stand-by section U is provided outside an outer cup 75 on a positivedirection side of an M direction (a right side in FIG. 42), and acleaning liquid supply nozzle 90 serving as a pH adjusting liquid supplysection which is capable of supplying, for example, two kinds ofcleaning liquids to a wafer W is on stand-by in the stand-by section U.

The cleaning liquid supply nozzle 90 is communicatingly connected to twostorage tanks 383 and 384 by a pipe 382, for example, as shown in FIG.43. In the storage tank 383, an alkaline cleaning liquid which isadjusted to have a predetermined pH value, for example, pH 10 is stored.The alkaline cleaning liquid is, for example, a pure water with thedeveloping solution added thereto. The predetermined pH value isdetermined based on a correlation curve as shown in FIG. 44 which isobtained from an experiment in advance, the correlation curve showingthe correlation between the zeta potential of insoluble substancesfloating in a liquid and the pH value of the liquid. A pH value at whichan absolute value of the zeta potential of the insoluble substancesbecomes a maximum value is selected.

In the storage tank 384, for example, a neutral cleaning liquid, forexample, a pure water is stored. As shown in FIG. 43, a three-way valve385 is provided in the pipe 382 at a branch point to the storage tank383 and the storage tank 384 so that the alkaline cleaning liquid andthe pure water can be selectively supplied to the cleaning liquid supplynozzle 90.

A developing method carried out in the developing unit 318 as structuredabove will be explained.

The wafer W carried into the developing unit 318 is held on a spin chuck60 by suction. When the wafer W is held by suction, a developing step ofthe wafer W is started. In this developing step, the developing solutionsupply nozzle 80 first moves to a start position S inside a cup 70 nearan edge portion of the wafer W on a negative direction side of the Mdirection and moves from the start position S to an end position E nearan edge portion of the wafer W on the positive direction side of the Mdirection while discharging the developing solution. By this operation,a predetermined amount of the developing solution is loaded on the waferW and static development for a predetermined period of time is started.In this static development, most of a resist film in exposed portionsdissolves in the developing solution, and a part of the resist filmturns into the insoluble substances to float in the developing solution.

When the developing step is finished after the static development isperformed for the predetermined period of time, a cleaning step of thewafer W is carried out. In the cleaning step, the cleaning liquid supplynozzle 90 first moves to a position above a center part of the wafer Wand the wafer W is rotated at a predetermined speed. Then, the alkalinecleaning liquid is first discharged from the cleaning liquid supplynozzle 90, thereby supplying the alkaline cleaning liquid of pH 10 ontothe wafer W. The developing solution on the wafer W is replaced with thealkaline cleaning liquid so that the liquid on the wafer W is maintainedat pH 10. In this manner, the zeta potential of the insoluble substancesin the liquid on the wafer is maintained, for example, at −70 mV asshown in FIG. 44 to maintain the absolute value of the zeta potential atthe maximum value. During this period, the cohesion of the insolublesubstances on the wafer W is inhibited and they are dispersed outsidethe wafer W by a centrifugal force.

After the alkaline cleaning liquid is supplied for a predeterminedperiod of time, the three-way valve 385 is switched over so that thepure water is in turn supplied onto the wafer W. This supply of the purewater completely stops the development of the resist film and completelyremoves the insoluble substances remaining on the wafer W as well. Aftera predetermined period of time elapses, the supply of the pure water isstopped to finish the cleaning step, and then the wafer W is rotated ata high speed so that the wafer W is dried by shaking-off. When thisdrying step is finished, the wafer W is delivered from the spin chuck 60to the main carrier 13 and the wafer W is carried out of the developingunit 318 so that a series of the developing treatment is finished.

According to this embodiment, since the alkaline cleaning liquid of pH10 is supplied in the cleaning step and the absolute value of the zetapotential of the insoluble substances on the wafer W is maintained atthe maximum value, an electrical repellent force among the insolublesubstances is kept so that the cohesion of the insoluble substances canbe prevented. Accordingly, the particle size growth of the insolublesubstances and the adhesion of the insoluble substances to the wafer Wand so on can be prevented. Consequently, development defects can bereduced. Further, since a cleaning time for removing the insolublesubstances and so on adhering to the wafer W is not required, the totaldeveloping treatment time can be shortened.

In addition, since the pure water is supplied after the alkalinecleaning liquid is supplied, the development of the resist film can becompletely stopped and the impurities such as the insoluble substancesremaining on the wafer W can be completely removed.

In the embodiment described above, the pH value of the liquid on thewafer W is adjusted by supplying the wafer W with the alkaline cleaningliquid whose pH value is adjusted in advance, but the pH value of theliquid on the wafer W may be adjusted by supplying the cleaning liquidand a pH adjusting liquid separately.

FIG. 45 shows an example of such a structure. A rinse arm 400 supports apure water supply nozzle 401 serving as a cleaning liquid supply sectionwhich supplies a cleaning liquid, for example, a pure water, and a pHadjusting liquid supply nozzle 402 serving as a pH adjusting liquidsupply section which supplies a pH adjusting liquid, for example, adeveloping solution. The pure water supply nozzle 401 and the pHadjusting liquid supply nozzle 402 are so supported by the rinse arm 400as to be movable to a position above the vicinity of the center of thewafer W.

The pure water supply nozzle 101 is communicatingly connected to a purewater supply unit 404 via a pipe 403, for example, as shown in FIG. 46,and the pH adjusting liquid supply nozzle 402 is communicatinglyconnected to a pH adjusting liquid supply unit 406 via a pipe 405. Thepure water supply unit 404 and the pH adjusting liquid supply unit 406have a pressure-sending mechanism such as a pump, a storage tank, and soon which are not shown so that the pure water and the pH adjustingliquid can be supplied to the respective nozzles 401 and 402 atpredetermined flow rates and at predetermined timing. As the pHadjusting liquid, for example, an ammonia water is used.

The supply flow rates of the respective liquids from the pure watersupply unit 404 and the pH adjusting liquid supply unit 406 arecontrolled by a control section 407. The control section 407 controlsthe supply flow rates of the respective liquids so that the liquid onthe wafer W, for example, in the cleaning step has a set pH value, forexample, pH 10.

Then, the pure water supply nozzle 401 and the pH adjusting liquidsupply nozzle 402 move to the position above the vicinity of the centerof the wafer W in the cleaning step which is carried out after thedeveloping step, and the pure water and the pH adjusting liquid aredischarged from the respective nozzles 401 and 402 onto the rotatedwafer W at the predetermined flow rates. The liquids discharged onto thewafer W and mixed with each other are maintained, for example, atapproximately pH 10 and the wafer W is cleaned in this state. After apredetermined period of time elapses, the supply of the pH adjustingliquid from the pH adjusting liquid supply nozzle 402 is stopped andonly the supply of the pure water from the pure water supply nozzle 401is carried out. Thereafter, the supply of the pure water is stopped andthe wafer W is dried by shaking-off similarly to the above-describedembodiment.

In this example, since the pure water and the pH adjusting liquid aredischarged from the nozzles exclusively used for the respective liquids,both of the liquids are not mixed in the nozzles or pipes so that stableliquid supply can be constantly realized. Further, in order to supplyonly the pure water onto the wafer W, what is required is only stoppingthe supply of the pH adjusting liquid, and therefore, thisswitching-over operation can be performed smoothly. Incidentally, the pHadjusting liquid is not limited to TMAH(N(CH₃)₄OH), and may be NH₄ orthe like.

In the above-described embodiment, the pH value of the liquid on thewafer W is so adjusted that the absolute value of the zeta potential ofthe insoluble substances becomes the maximum value, but the pH value ofthe liquid on the wafer W may be so adjusted that the absolute value ofthe zeta potential of the insoluble substances becomes a value equal toor larger than a predetermined value at which the insoluble substancesdo not cohere together.

In such a case, for example, as shown in FIG. 44, a predetermined valueV₀ being the minimum absolute value of the Zeta potential at which theinsoluble substances do not cohere together and a pH range, for example,pH 8 to pH 14, in which the absolute value of the zeta potential of theinsoluble substances can be maintained at a value equal to or largerthan the predetermined value V₀ are obtained in advance. Then, thecleaning liquid whose pH value is adjusted to pH 8 which falls withinthe aforesaid pH range is supplied onto the wafer W in the cleaningstep. This prevents the cohesion of the insoluble substances andinhibits the particle size growth of the insoluble substances and theadhesion of the insoluble substance to the wafer W, so that developmentdefects can be reduced.

In the above-described embodiment, the present invention is applied tothe developing method of the wafer W, but the present invention is alsoapplicable to developing methods of substrates other than semiconductorwafers, for example, LCD substrates, mask reticle substrates forphotomask, and so on.

According to the present invention, the particle size growth of theinsoluble substances floating in the developing solution at the time ofthe developing treatment can be restrained and the adhesion of theinsoluble substances to the substrate can be prevented so thatdevelopment defects caused by this adhesion and so on can be reduced.Accordingly, yields can be improved. Further, since the cleaning timefor removing the insoluble substances adhering to the substrate is notrequired, the developing treatment time is shortened to achieveimprovement in throughput.

1-64. (canceled)
 65. A developing unit performing a developing step ofsupplying a developing solution to a substrate and thereafter, acleaning step of supplying a cleaning liquid onto the substrate,comprising: a pH adjusting liquid supply section supplying a pHadjusting liquid onto the substrate in order to adjust a pH value of aliquid on the substrate during said cleaning step to a predetermined pHvalue, wherein the predetermined pH value is set based on a correlationcurve, prepared in advance, of the pH value of the liquid on thesubstrate and a zeta potential of insoluble substances in the liquid, soas to make an absolute value of the zeta potential of the insolublesubstances maximum.
 66. A developing unit according to claim 65, furthercomprising: a cleaning liquid supply section supplying a cleaning liquidto said substrate, being disposed independently from said pH adjustingliquid supply section; and a control section controlling supply flowrates of the liquids respectively from said pH adjusting liquid supplysection and said cleaning liquid supply section. 67-69. (canceled)
 70. Adeveloping unit performing a developing step of supplying a developingsolution to a substrate and thereafter, a cleaning step of supplying acleaning liquid onto the substrate, comprising: a pH adjusting liquidsupply section supplying a pH adjusting liquid onto the substrate inorder to adjust a pH value of a liquid on the substrate during saidcleaning step to a predetermined pH value, wherein: the predetermined pHvalue is set based on a correlation curve, prepared in advance, of thepH value of the liquid on the substrate and a zeta potential ofinsoluble substances in the liquid, so as to make an absolute value ofthe zeta potential of the insoluble substances equal to a set value orhigher; and the set value is equal to or higher than a lowest value atwhich the insoluble substances start to cohere together.
 71. Thedeveloping unit according to claim 70, further comprising: a cleaningliquid supply section supplying a cleaning liquid to said substrate,being disposed independently from said pH adjusting liquid supplesection; and a control section controlling supply flow rates of theliquids respectively from said pH adjusting liquid supply section andsaid cleaning liquid supply section.